This invention relates to heat exchangers using peristaltic pumps to circulate a separate fluid on opposite sides of a heat-conductive wall and enhance heat transfer rates between the fluids. In the prior art there are many types of peristaltic pumps; Bogachev U.S.S.R., Pat. No. 118704 discloses a pump using an elastic casing squeezed from opposite sides by spherical rollers whereby the casing is extended to sealing contact, generating a peristaltic pumping action; in a second version, cylindrical rollers deflect a double-convex casing to sealing contact but also spreads the casing laterally: This is unlike the invention; in Bogachev's patent there is no possibility of heat-exchange between two fluids. Other peristaltic pumps roll-down a flexible tubing or deform it rythmically with cam-actuated fingers to move a fluid, substantially unlike the invention. Peristaltic pumps also generally have high running friction, short life of the elastomer and low speed and pressure output, deficiencies substantially overcome by the invention. Heat exchangers are not known to use peristaltic pumps and most often are passive elements where fluids must be circulated by outside means; also heat transfer rates suffer by incomplete turbulence of the fluids. Peristaltic pumping of the invention substantially overcomes these deficiencies.